RE: xalan processor problem

This isn't strictly an xslt question but more of a processor problem.
Since changing version of xalan to the latest one the relative doctype
declaration i.e.

<?xml version="1.1"?>
<!DOCTYPE greeting SYSTEM "hello.dtd">
<greeting>Hello, world!</greeting> 

comes up with 

Run-time exception error; current exception: MalformedURLException
        An exception can only be re-thrown in a handler.
Abort - core dumped

To my understanding from the xml spec a uri can be both relative and full.

has anyone come across this or know why.
Thanks for any help.
Andrew Curry